PROC. BIOL. SOC. WASH. 107(2), 1994, pp. 383-390 A NEW HEMICHORDATE, SACCOGLOSSUS BROMOPHENOLOSUS (HEMICHORDATA: ENTEROPNEUSTA: HARRIMANIIDAE), FROM NORTH AMERICA Gary M. King, Cem Giray, and Irv Komfield Abstract. —A new species, S. bromophenolosus, is distinguished from its con-gener, S. kowalevskii (Agassiz 1873), on the basis of the following morpholog-ical, biochemical, and genetic criteria: placement of gill pores; prominence of the dorsal ridge; structure of the proboscis skeleton; presence of bromophenols or bromopyrroles; relative electrophoretic mobility of allozymes (e.g., super-oxide dismutase); molecular weights of fragments from restriction endonuclease digestion of mitochondrial DNA. S. bromophenolosus occurs from southern Maine, U.S.A., to Nova Scotia, Canada, with an additional record from Willapa Bay, Washington, U.S.A. Three families of enteropneusts (Hemi-chordata: Enteropneusta: Harrimaniidae, Ptychoderidae, and Spengeliidae) occur along the coasts of North America (Milne & Milne 1973, Bullock 197.S, Ruppert & Fox 1988). The best known species belong to the genus Saccoglossus (Harrimaniidae), which occurs on both the Atlantic and Pa-cific coasts (Milne & Milne 1973, Bullock 1975). Of the several saccoglossids, S. ko-walevskii (Agassiz 1873) has been described in greatest detail. Various aspects of its dis-tribution, biology and ecology have been reported subsequent to Agassiz's (1873) ini-tial description (e.g., Bateson 1886, Bullock 1940, Tweedell 1961, Colwin & Colwin 1962, Barrington 1965, King 1986, Woodin et al. 1987, Balser & Ruppert 1990, Carey & Mayer 1990). S. kowalevskii has been considered the only member of its genus on the Atlantic coast of North America, and has been noted in intertidal collections from Nova Scotia to Georgia (Dorjes 1972, Bromley 1979). Although there are certain characteristics common to all saccoglossids along this range, a comparison of biochem-ical attributes reported for populations from Maine and South Carolina has raised ques-tions about the taxonomic status of the spe-cies (King 1986, Woodin et al. 1987). Spe-cifically, animals collected in Maine and northward typically accumulate high con-centrations of two secondary products, 2,4-dibromophenol and a dibromoindole (King 1986, unpubl. data), while animals from other locales accumulate 2,3,4-tribromo-pyrrole (King, unpubl. data, Woodin et al. 1987). The differential accumulation of these haloaromatics does not appear to correlate with any major environmental variables or gradients. Further, the presence of a given haloaromatic phenotype appears to be a fixed trait associated with populations from specific regions. We now report that the genus Saccoglos-sus consists of at least two distinct species along the Atlantic coast of North America. These two species are readily differentiated by gross external morphological characters, the accumulation of halogenated aromatic compounds, morphology of the proboscis skeleton, electrophoretic mobilities of sev-eral enzymes, and the sequence composi-tion of the mitochondrial DNAs (mtDNA). We propose the name S. bromophenolosus for the new species occurring from southern